If you are asking about groups as a sociological concept, then groups have four major features that help us to identify them as groups.
- To state the obvious, there must be more than one person in a group.
- The people must interact with one another. This differentiates groups from simple aggregations of people. For example, people who are all on the same airplane are an aggregation but not really a group because they do not all interact with one another. This also differentiates groups from social categories. Women or African Americans, for example, are not a group from the perspective of sociology.
- They must have shared expectations of some sort. These are expectations about what sorts of behaviors are and are not acceptable within the context of the group.
- Finally, they must have a sense of common identity. That is, they must perceive that they all have something in common (all cheer for the same sports team, all interested in chess, all oppose abortion) that makes them similar to one another.
In sociology, we can identify groups by determining whether they have all of these characteristics.